Method of refining distillates



Patented Jan. 1932 UNITED STATES PATENT OFFICE PARRY BbRGSTROM, oF wAsfiINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TO LAWRENCE L. REEVES, OF WASHINGTON, DISTRICT OF COLUMBIA,

METHOD OF REFINING DISTILLA'IES No Drawing.

This invention relates to a method of treatment for refining petroleum distillates, and among its objects it seeks to provide an effective method for sweetening such distillates,

'5' improving their color, and also facilitating the removal of certaincompounds (principally the gum forming compounds) which detract from the value of the distillate as a fuel, or for other known uses.

It is well known that petroleum distillates, and especially those that are produced by socalled cracking methods, require certain refining treatments before they can be rated a commercial product. The raw distillates are generally treated for the removal of those compounds which give color, odor, and sourness to the product; and also for removal of gums and organic gum forming constituents .as are found to exist in practically all raw distillates and particularly those produced by vapor phase cracking and Which contain high percentages of the unsaturated hydrocarbons. The present invention provides a cheap and effective method for correcting sourness and improving the color of distillates, andafiiords substantial aid in conjunction with certain known methods for removal of gum, and gum and resin-forming compounds, to the end that-these methods of refining are made more effective and can be accomplished in a shorter period of time, with substantial saving in ex pense.

For improving distillates as to odor and sweetness, the usual treatment is with .the doctor solution (sodium plumbite) by which at least some of the soluble sulphur compounds that impart odor and sourness to the distillate are either removed or precipitated. Some of these soluble compounds (secondary mercaptans) however, do not respond to the doctor. treatment which must be supplemented by the addition of suitable quanti ties of elemental sulphur, in order to convert remaining mercaptans into non-corrosive compounds (disulphides), Care is required in the use of sulphur in this supplemental treatment, since any excess over actual need or requirements constitutes an undesirable element in the distillate, and which may be convertible into SO which is corrosive. The

duces into the distillate a chemical reagent Application filed March 18, 1930. Serial No. 436,894.

"treated distillate must .next be washed or scrubbed with water to remove any traces of acid. The acid treatment involves an actualloss in distillate due to reaction of some of the useful constituents with the acid, and this treatment is moreover expensive by reason of the cost of the reagent.

It is generally accepted, according to authorities, that sourness in petroleum distillates is due in large part, if not entirely, to the presence of mercaptans in solution in the distillate. With the doctor treatment, and augmented by addition of elemental sulphur, it is possible to change or convert to disulphides practically all the mercaptans responsible for the sourness of the distillate. Appreciative of the fact, however, that in treating with the doctor solution, and adding sulphur, in refining operations, one intro- (sulphur) which must, or should be, subse- 80 quently removed, the problem has been to discover a different method of treatment to accomplish the desired result, and preferably a method which avoids the use of chemical reagents which in themselves may be, or in fact are, added impurities or compounds injurious to the final product if not entirely removed.

It has been discovered that a cracked petroleum distillate such e. g. as naphtha,if exposed for an appropriate length of time to actinic or ultra-violet light. or to oxidizing conditions, will be found to have undergone certain chemical changes by which soluble organic peroxides are formed in quantities proportional to the degree and extentof its exposure to the oxidizing or catalytic agents. These peroxides are also found in distillates which have been stored (weathered) with no v speclal provlsions for treatment as above outlined, and where auto-oxidation is probably responsible for the peroxide formation,

naphtha containing ethyl mercaptan, and

sour to the doctor test was treated with 5 cc. of cyclohexene containing soluble organic peroxides. The reaction proceeds readily at ordinary room temperature, and with only slightagitation, the result being a distillate from which all trace of sourness is removed,

and which is sweet to the doctor test.

. The same result is obtained in the treatment of sour distillates containing secondary amylor secondary octyl-mercaptans with a hydrocarbon distillate which contains organic peroxides.

In addition to the sweetening action, l have discovered that the peroxide treatment is also an efiective aid in the elimination oi other sulphur compounds that may be present in the distillate and principally those in the form of sulphides. The peroxide reagent will convert these sulphides into water-soluble sulphones which may then be removed by such a simple step as a water wash or by steam quent to the ,which occurs between in the aqueous distillation.

As is apparent from the specific example given, only small amounts of'the reagent dis tillate are required in order to sweeten a relatively large quantity of sour distillate. Calculations based upon a reaction similarto that H 0 and mercaptans, show that only approximately 0.18 lbsnof cyclohexene peroxide are required'as the sweetener for lbs. of distillate containing t;

of one per cent or an average quantity of mercaptans that make for sourness of the distillate. I find, in my experiments, that all mere captans respond to the peroxide treatment, and that in using this treatment for sweetening, the addition of elemental sulphur, as doctor treatment is avoided.

It will be apparent therefore, that my discovery may entirely replace theusualdoctor treatment; or that it may be used in conjunction therewith to remove such secondary mercaptans as are not reached by the doctor wash. However, in the practice of my invention in conjunction with a doctor wash treatment, a fraction, distillate, or other petroleum hydrocarbon which is known to contain organic peroxides may be added to the fraction undergoing treatment and subsedoctor wash, in lieu ofadding elemental sulphur, to form the disulphides. The obvious advantage of the combined neaaaee avoid adding elemental sul- The further discovery that I have made i in the practice of my invention is the combining of the peroxide treatment with a fullers earth treatment, the latter being the 4 now known method of removing discolorizing, gum, and gum forming compounds. Thus for example, I may react the peroxide distillate, in a tower or chamber through which the distillate under treatment is being passed, and in contact with the earth of clay in said tower or chamber.. This may be done in either the liquid or vapor phase; or the distillate to be treated may be in vapor phase and the peroxide distillate may be in liquid phase. In the practice or such methods, it is possible in the single step to sweeten a cracked distillate as well as to re-= move the diolefins (as by polymerizing) where the distillate undergoing refinement sis tr ated in thev apor phase. In this method, temperature control is usually. necessary to the extent at least that the operative zone in the tower or chamber where the peroxidedistillate is to be effective should be kept at a temperature sufiiciently low to preclude destruction of the peroxides. T have found that conjoint use of the peroxide treatment and fullers earth and, or, bauxite has the advantage thatany excess of peroxide reagent that may be used will be effectively decomposed by the earth or clay, and thereby minimize the chance of the, peroxides being carried over into the refined product Tn liquid phase treatments, combining the peroxide, and earth or clay treatments, the peroxide distillate is found to have a beneficial-efiect on the earth'or clay used, which I is manifest by the fact that the length of time that the earth or clay may be used before losing its eiiectiveness is materially in creased I Many other applications and uses of my invention in the refining of petroleum distillates will be apparent to one skilled in the art, and it is not intended that the specific disclosures and examples given-shall limit the scope of the invention.

lVhat 1: claim as my invention and desire to cover by Letters Patent is set forth as follows: i

1. The step in refining a petroleum distillate containing mer'captans comprising react+ ing' with said distillate another distillate in which organic peroxides have been developed. 2. The step'in refining a petroleum fraction containing mercaptans comprising reacting with said fraction a petroleum hydrocarbon in which organic peroxides have formed.

3. The step in refining a sour petroleum distillate containing unsaturated hydrocarbons comprising reacting with said distillate another similar distillate which has been tgeated for the development of organic perox- 1 es.

4. The method of refining cracked sour pe troleum distillates to change the mercaptans that are present to compounds that are sweet and non-corrosive, comprising weathering a distillate for the purpose of forming soluble organic peroxides therein and treating the cracked distillate with a quantity of the weathered distillate containing the said soluble organic peroxides.

5. The method of claim 4 in which the quantity of peroxide solution is substantially 2% by weight of the distillate to be treated.

6. The method of refining sour cracked petroleum distillates comprising contacting the distillate with fullers earth and while mainproducts with an organic peroxide solution formed by the action of light and oxygen on a distillate or fraction containing unsaturated hydrocarbons.

8. process for sweetening sour petroleum products comprising the step of treating such formed by auto-oxidation of a distillate or fraction resulting from a cracking operation.

9. A process for sweetening petroleum distillates containing mercaptans that are sour comprising the step of treating such products with a cracked distillate in which organic peroxides have formed, and subsequently contacting the mixture of distillates with fullers earth.

10. The method of refining cracked petroleum fractions in Vapor phase which fractions contain mercaptans comprising contacting the fraction with another fraction in which organic peroxides have formed, while maintaining the temperature condition of the contacting zone somewhat below the temperature of dissociation of the organic peroxides.

11. The method of claim 10 in which the contacting of the fractions is accomplished in the presence of a material such for example as fullers earth.

122. The method of claim 10 to be followed by the step of condensing the mixed vapor fractions and treating the condensate by contact with fullers earth.

13. The method of refining a cracked petroleum distillate containing mercaptans comprising contacting the distillate in vapor phase with fullers earth and simultaneously have formed.

PARRY BQRGSTBOM.

products with an organic peroxide solution 

